Production of chromic chloride



' tively non-volatile chloride is low.

Patented Apr. 29, 1941 PRODUCTION OF CHROMIC CHLORIDE Irving E. Muskat, Akron, Ohio, assignor to Pitts. burgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania Application December 23,1939, Serial No. 310,710

11 Claims.

This'invention relates to the chlorination of chromium bearing materials and is particularly adapted to the chlorination of chromium ores, such as chromite, which contain chromium in concentrations generally in excess of ten percent by weight and preferably in excess of twenty percent.

In the chlorination of such ores, it has been found desirable to conduct the chlorination at a temperature sufficiently high to cause formation and vaporization of chromic chloride and prior to the present invention, it has been considered essential to conduct the reaction in a heated retort or furnace. This process has required the use of receptacles made of materials of high heat conductivity and in general, such materials oxygen may be avoided, and control of the reaction is somewhat simplified.

While the process may be conducted in numerous typos of reactors, I have found that it is generally desirable to conduct the chlorination in a shaft furnace or similar device. This furnace may be constructed of heat resistant mahave been found to be attacked very rapidly by 4 chlorine at the temperature of operation. Accordingly, the prior art does not appear to describe a process for effectivelychlorinating chro-' mite ores to manufacture chromic chloride upon a commercial scale.

In accordance with my invention, I have found that'the chlorination of these materials might be conducted without recourse to an externally heated reactor. I have found that if the chlorination is conducted at a temperature not substantially less than 850 C. and preferably in excess of 950 C., the reaction proceeds with considerable rapidity and that by regulation of the rate of introduction of ore, carbon, or other reducing agent, particularly carbonaceous reducing agent, and chlorine into the reactor, it is possible to generate sufiicient heat by means of the reaction to maintain the temperature at its proper value. This does not appear to be possible at lower temperatures.

The process is particularly effective in the treatment of ores wherein the content of magnesium or other material which forms a rela- As described in a copending application filed by myself and terials such as firebrick, alundum brick, or other refractory material and may be designed for the purpose of conserving as much heat as possible.

In general, it is found to be desirable to chlorinate a mixture of ore and carbon or other suitable reducing agent. The ore may be of any convenient size and form but it is preferably ground to a suitable value, for example, to minus mesh, and is then mixed with a suitable carbon containing materials, such as coal coke, petroleum coke, charcoal, peat, sawdust, or other carbonaceous reducing agent (such as carbon monoxides, etc. The mixture may be bonded with suitable bo'nding agents, such as molasses, tar, asphalt, etc., and formed into briquettes, or it may be treated without the use of such bonding agents.

The accompanying drawing diagrammatically illustrates a suitable apparatus for operating the process in accordance with the present invention. The apparatus comprises a suitable shaft furnace l, which may be constructed from firebrick or other resistant material and which is provided with chlorine tuyeres 6, furnace inlet 2, to which ore is supplied by means of a feed mechanism 3, and an outlet for vaporized gas 1. In the ordinary operation of this device, suitable mixtures of chromium ore and carbon in the form of briquettes or as finely ground material is supplied to hopper 5, and is fed into the furnace through inlet 2, by means of the star feeding mechanism 4. At the same time, chlorine is introduced through tuyeres 6, and the vaporized iron and chromic chlorides escape through outlet 1, and are led into a suitable condensing system, not shown. Unchlorinated ore is withdrawn from the base of the furnace which is provided with a suitable door or closure 8.

In order to initiate the process, the furnace is preheated in a convenient manner to a temperature of approximately 850 C., or above. This may be done suitably by introducing and burning a charge of coke, coal, natural gas, or similar carbonaceous material within the furnace. When the temperature within the furnace has been raised to the required temperature a charge comprising a, mixture of ore and carbon, preferably reaction. Further charges of briquettes are ill-- troduced as the reaction proceeds and by regulation of ore, chlorine and carbon, it is possible to maintain the process in continuous operation without application of external heat to the furnace. Ordinarily, the regulation of the rate of introduction of ore, carbon and chlorine is conducted in accordance with periodic and continuous observation of the temperature within the reactor. Thus, if the temperature begins to decrease, the rate of introduction of the chlorine, ore and carbon may be increased, while if the temperature increases to an undesirable value, the rate of introduction of ore, chlorine and carbon may be decreased correspondingly. The temperature also may be regulated to some degree by conducting the rate of withdrawal of the chlo-.

rinated residue since a large amount of heat'may be dissipated by rapid removal of the residue and the reactor cooled by cool incomingore.

If dificulty is encountered in maintaining the temperature by heat of the chlorination reaction,

the heat developed during the reaction is such that the temperature of the reaction zone is too high for continuous operation. This reaction zone may be cooled, if desired, by introduction of a diluent gas, such 'as nitrogen or carbon dioxide.

The carbon concentration of the ore mixture may be varied in accordance with the composition of the ore and the temperature desired. In gen- 'eral, when the ore contains high concentrations of chromium and iron, the carbon concentration may be correspondingly high, and vice verse... Carbon concentrations in excess of 5% are generally found to be desirable and in treating chromium ores such as chromite containing to of ClzOs for vaporization of both iron and chromium chlorides, it is found that optimum results may be obtained by using 5 to 25% by weight of carbon based on the weight of the ore introduced.

In many cases it'is found desirable to utilize a gaseous reducing agent in lieu of all or'a portion of the carbon, carbonaceous material or other solid reducing agent. Thus, such agents as carbon monoxide, hydrogen, methane, ethane, carbon tetrachloride, sulphur chloride, phosgene, sulphur vapor, etc. may be introduced into the reaction mixture generally with the chlorine and the ore introduced may contain carbon in smaller concentration than would otherwise be used or may contain no carbon whatsoever. By use of such agents it is possible to avoid sintering in treating ores which normally sinter to an objectionable degree. Thus, where substantial magable amounts it is found that a larger portion of the chloride isvaporized. This is probably due to the presence of a substantially greater volume in zones within the furnace wherein magnesium or similar sintering chloride tends to accumulate whereby the chloride is carried over into the condensing system.

The volume of gaseous reducing agent is capable of variation in accordance with the ore undergoing treatment and the amount of carbon present. In the case of carbon monoxide it is generally desired to use equal volumes of chlorine and carbon monoxide and, in general, the total reducing agent should be sufflcient to theoreticalnesium or similar chloride is formed in objectionassua e ly reduce the iron and chromium oxides to the metallic state. -'I'he gaseous reducing agent may be introduced separately into the furnace, preferably in a lower portion thereof, or it may be mixed with the chlorine.

The following examples are illustrative:

Example l.-A quantity of briquettes /4 to 1 inch in diameter was prepared from a mixture of parts by weight of ore, 12 parts by weight of ground coke, 8 parts by weight of sawdust, and 12 parts by weight of molasses, by firing at 500 C. until .the volatile hydrocarbons were substantially removed. The carbon content of the briquettes was about 17 percent of the weight of the bri= g ugttes. The ore contained 47% CrzOa and 24% A shaft furnace, having an internal diameter of 10 inches was preheated by a coke fire within the shaft at 1000 C. At this time a charge of briquettes was added and chlorine was introduced into the base of the shaft to initiate the chlorination reaction. The process was carried on continuously for many hours by introducing briquettes at a rate of 0.20 kg. per minute, chlorine at a rate of liters per minute. ture remained at about 1000" C. throughout the reaction and the chloride vapors given ofi were recovered and fractionally condensed to recover chromium and ferric chloride.

Example II.A quantity of briquettes A to 1 inch in diameter were prepared from a mixture of 100 parts by weight of ore, 8 parts by weight of sawdust, and 12 parts by weight of molasses, by firing at 500 C. until the volatile hydrocarbons were substantially removed. The ore contained 42% CrzOa, 22% FeO and 16% MgO.

A shaft furnace having an internal diameter of 10 inches was preheated by a coke fire within the shaft at 1000 C. At this time a charge of briquettes was added and chlorine and carbon monoxide were introduced into the base of the shaft to initiate the chlorination reaction. The process was carried on continuously for many hours by introducing briquettes at a rate of 0.20 kg. per minute, chlorine at a rate of 130 liters per minute and carbon monoxide at a rate of liters per minute. The temperature remained at about 1000 C. throughout the reaction and the chloride vapors given ofi were recovered and fractionally condensed to recover chromium and ferric chloride.

Hydrogen chloride, phosgene, or other gaseous chlorinating agents may be used in conjunction with chlorine, or in lieu thereof, in accordance with this invention.

Although this invention has been described with reference to specific details of certain embodiments thereof, it is not intended that such details shall be regarded as limitations upon the scope of the invention except insofar as included in the accompanying claims.

I claim:

1. A continuous method of chlorinating a mite ore containing in excess of 10 percent The temperaand carbon into the reactor at such a rate that suflicient heat is evolved from the reaction to maintain the temperature at not less than 950 C. without externally heating the zone, whereby chromium chloride is formed and volatilized.

3. A continuous process of chlorinating chromite ore which contains in excess of 10 percent chromium which comprises chlorinating a mixture of said ore and about to 25 percent by weight of carbon in the reaction zone of a reactor and introducing chlorine, carbon and ore into the reaction at such a rate that suflicient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone, whereby chromium chloride is formed and volatilized.

4. A continuous method of chlorinating a chromium bearing ore containing in excess of percent chromium which comprises chlorinating said ore in the presence of a reducing agent in the reaction zone of a reactor and introducing said ore, chlorine and reducing agent into the reactor at such a rate that sufficient heat is.

evolved from the reaction to maintain'the temperature at not less than 850 C. without externally heating the zone, whereby chromium chloride is formed and volatilized.

5. A continuous method of chlorinating a chromium bearing ore containing in excess of 10 percent chromium which comprises chlorinating said ore in the presence of a carbonaceous material in the reaction zone of a reactor and introducing said ore, chlorine and carbonaceous material into the reactor at such a rate that sufficient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone, whereby chromium chloride is formed and volatilized.

6. A continuous method of chlorinating chromium ore containing in excess of 10 percent chromium which comprises conducting the chlorination in the presence of a gaseous reducing ent in the reaction zone of a reactor and introducing said ore, gaseous reducing agent and chlorine at such a rate that suflicient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone whereby chromium chloride is formed and volatilized.

7. A continuous method of chlorinating chromium ore containing in excess of 10 percent of chromium which comprises conducting the chlorination in the presence of carbon and a gaseous reducing agent in the reaction zone of a reactor and introducing said ore, carbon and gaseous reducing agent and chlorine at such a rate that suflicient heat is' evolved from the reaction to maintain thetemperatureat not less than 850 C. without externally heating the zone whereby chromium chloride is formed and volatilized.

8. A continuous method of chlorinating chromium ore containing in excess of 10 percent chromium which comprises conducting the chlorination in the presence of carbon monoxide in the reaction zone of a reactor and introducing said ore, carbon monoxide and chlorine at such a rate that sufficient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone whereby chromium chloride is formed and volatilized.

9. A method of chlorination which comprises forming a pervious bed of a chromium ore containing in excess of 10 percent chromium, introducing chlorine and a gaseous reducing agent into a lower portion of said bed to cause chlorination of the ore and fresh ore into an upper portion thereof and introducing the ore, chlorine and reducing agent at such a rate that suflicient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone, whereby chromium chloride is formed and volatilized.

10. A method of chlorination which comprises forming a pervious bed of a chromium ore containing in excess of 10 percent chromium, introducing chlorine and carbon monoxide into a lower portion of said bed to cause chlorination of the ore and fresh ore into an upper portion thereof and introducing the ore, chlorine and carbon monoxide at such a rate that sufiicient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone, whereby chromium chloride is formed and volatilized.

11. A continuous method of chlorinating a chromite ore containing in excess of 10 percent chromium which comprises chlorinating a mixture of said ore and at least about 17 percent of carbon in the reaction zone of a reactor and introducing said ore, chlorine and carbon into the reactor at such a rate that suflicient heat is evolved from the reaction to maintain the temperature at not less than 850 C. without externally heating the zone,,whereby chromium chloride is formed and volatilized.

IRVING E. MUSKAT. 

